1. Field of the Invention
The present general inventive concept relates to an inkjet image forming apparatus and a maintenance method thereof, and more particularly, to an inkjet image forming apparatus employing an array inkjet head having a nozzle unit having a length corresponding to a width of a printing medium in a main scanning direction, and a preliminary spitting method thereof.
2. Description of the Related Art
Inkjet image forming apparatuses form an image by firing ink from an inkjet head (e.g., shuttle type inkjet head) onto a sheet of paper while reciprocating the inkjet head in a main scanning direction and feeding the paper in a subscanning direction. For high speed printing, recent inkjet image forming apparatuses use an inkjet head (e.g., array inkjet head) with a nozzle unit having a length corresponding to a width of the paper in the main scanning direction instead of using the shuttle type inkjet head. In these inkjet image forming apparatuses, the array inkjet head is fixed, and only the paper is fed in the subscanning direction. Therefore, the inkjet image forming apparatus can have a simple driving mechanism and provide the high speed printing. In these inkjet image forming apparatuses, when a printing margin in a width direction of the A4 size paper is not considered, the nozzle unit is about 210 mm long so as to correspond to the width of A4 the size paper. Viscosity of ink should be kept in an appropriate state for printing. If the printing is not performed for a while, moisture of ink in the nozzle is vaporized and therefore the viscosity of ink increases. Also, while the printing is performed, the moisture of the ink in the nozzle that does not participate in the printing is vaporized and therefore the viscosity of the ink increases. Under this circumstance, ink may not be ejected from the nozzle. To prevent this, a preliminary spitting that before a printing is performed or after a predetermined amount of printing is performed, ink is spitted a few times to remove the ink with a high viscosity is performed. At this time, fog (particles) of the spitted ink is dispersed into an inside of the inkjet image forming apparatus. The shuttle type inkjet head has a few tens of nozzles while the array type inkjet head has more than a few thousands of nozzles. In the case of the array type inkjet head, the fog of ink may be generated so much, which may contaminate an inside of the image forming apparatus.